Among pipe couplings comprising female and male coupling members, there has been developed a pipe coupling wherein one of the two coupling members has a valve unit axially slidably set in a through-hole thereof, and the valve unit is moved backward and forward in response to coupling and decoupling between the two coupling members to open and close a fluid path in the coupling member (see Japanese Patent Application Publication No. 2005-127376).
Specifically, the valve unit is urged axially forward by a spring member toward a closed position for closing the fluid path. When the two coupling members are coupled to each other, one coupling member pushes the valve unit of the other coupling member thereinto against the urging force of the spring member to an open position for opening the fluid path. When the two coupling members are decoupled from each other, the valve unit is returned to the closed position by the urging force of the spring member. The valve unit has a fluid path extending in the axial direction of the through-hole of the coupling member. In response to the valve unit being moved axially backward and forward, a rotary valve member provided in the valve unit is rotated by a cam mechanism to open and close the fluid path.
The rotary valve member has a spherical seal surface on a part of the outer peripheral surface thereof. When the two coupling member are not coupled to each other, the seal surface sealingly engages all around a valve seat formed to surround the fluid path, thereby closing the fluid path. When the coupling members are coupled together and consequently the valve unit is moved backward, the rotary valve member is rotated, causing the seal surface to be displaced relative to the valve seat while sliding against it. As a result, the sealing engagement of the seal surface all around the valve seat is free to open the fluid path.